/*
* Copyright (c) 2002 Apple Computer, Inc. All rights reserved.
*
* @APPLE_LICENSE_HEADER_START@
*
* This file contains Original Code and/or Modifications of Original Code
* as defined in and that are subject to the Apple Public Source License
* Version 2.0 (the 'License'). You may not use this file except in
* compliance with the License. Please obtain a copy of the License at
* http://www.opensource.apple.com/apsl/ and read it before using this
* file.
*
* The Original Code and all software distributed under the License are
* distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
* EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
* INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
* Please see the License for the specific language governing rights and
* limitations under the License.
*
* @APPLE_LICENSE_HEADER_END@
*/
#define ASSEMBLER
#include <mach/ppc/asm.h>
#undef ASSEMBLER
#define __APPLE_API_PRIVATE
#include <machine/cpu_capabilities.h>
#undef __APPLE_API_PRIVATE
/* We use mode-independent "g" opcodes such as "srgi". These expand
* into word operations when targeting __ppc__, and into doubleword
* operations when targeting __ppc64__.
*/
#include <architecture/ppc/mode_independent_asm.h>
// *****************
// * S T R L C P Y *
// *****************
//
// size_t strlcpy(char *dst, const char *src, size_t size)// We optimize the move by doing it word parallel. This introduces
// a complication: if we blindly did word load/stores until finding
// a 0, we might get a spurious page fault by touching bytes past it.
// To avoid this, we never do a "lwz" that crosses a page boundary,
// or store unnecessary bytes.
//
// The test for 0s relies on the following inobvious but very efficient
// word-parallel test:
// x = dataWord + 0xFEFEFEFF
// y = ~dataWord & 0x80808080
// if (x & y) == 0 then no zero found
// The test maps any non-zero byte to zero, and any zero byte to 0x80,
// with one exception: 0x01 bytes preceeding the first zero are also
// mapped to 0x80.
//
// This algorithm is doubleword parallel in 64-bit mode.
.text
.globl EXT(strlcpy)
.align 5
LEXT(strlcpy) // size_t strlcpy(char *dst, const char *src, size_t size)#if defined(__ppc__)
lis r6,hi16(0xFEFEFEFF) // start to generate 32-bit magic constants
lis r7,hi16(0x80808080)
ori r6,r6,lo16(0xFEFEFEFF)
ori r7,r7,lo16(0x80808080)
#else
ld r6,_COMM_PAGE_MAGIC_FE(0) // get 0xFEFEFEFE FEFEFEFF from commpage
ld r7,_COMM_PAGE_MAGIC_80(0) // get 0x80808080 80808080 from commpage
#endif
mr r9,r3 // use r9 for dest ptr (must return r3 intact)
beq Laligned // source is aligned
subfic r0,r0,GPR_BYTES // r0 <- #bytes to align source
// Copy min(r0,r5) bytes, until 0-byte found.
// r0 = #bytes we propose to copy (NOTE: must be >0)
// r4 = source ptr (unaligned)
// r5 = length remaining in buffer (may be 0)
// r6 = 0xFEFEFEFF
// r7 = 0x80808080
// r9 = dest ptr (unaligned)
Lbyteloop:
cmpwi r5,0 // buffer empty?
beq-- L0notfound // buffer full but 0 not found
lbz r8,0(r4) // r8 <- next source byte
subic. r0,r0,1 // decrement count of bytes to move
addi r4,r4,1
subi r5,r5,1 // decrement buffer length remaining
stb r8,0(r9) // pack into dest
cmpwi cr1,r8,0 // 0-byte?
addi r9,r9,1
beq cr1,L0found // byte was 0
bne Lbyteloop // r0!=0, source not yet aligned
// Source is aligned. Loop over words or doublewords until end of buffer. We
// align the source, rather than the dest, to avoid getting spurious page faults.
// r4 = source ptr (aligned)
// r5 = length remaining in buffer
// r6 = 0xFEFEFEFF
// r7 = 0x80808080
// r9 = dest ptr (unaligned)
Laligned:
srgi. r8,r5,LOG2_GPR_BYTES// get #words or doublewords in buffer
addi r0,r5,1 // if no words, compare rest of buffer
beq-- Lbyteloop // r8==0, no words
mtctr r8 // set up word loop count
rlwinm r5,r5,0,GPR_BYTES-1 // mask buffer length down to leftover bytes
b LwordloopEnter
// Move a word or doubleword at a time, until one of two conditions:
// - a zero byte is found
// - end of buffer
// At this point, registers are as follows:
// r4 = source ptr (aligned)
// r5 = leftover bytes in buffer (0..GPR_BYTES-1)
// r6 = 0xFEFEFEFF
// r7 = 0x80808080
// r9 = dest ptr (unaligned)
// ctr = whole words or doublewords left in buffer
.align 5 // align inner loop, which is 8 words long
Lwordloop:
stg r8,0(r9) // pack word or doubleword into destination
addi r9,r9,GPR_BYTES
LwordloopEnter:
lg r8,0(r4) // r8 <- next 4 or 8 source bytes
addi r4,r4,GPR_BYTES
add r10,r8,r6 // r10 <- word + 0xFEFEFEFF
andc r12,r7,r8 // r12 <- ~word & 0x80808080
and. r11,r10,r12 // r11 <- nonzero iff word has a 0-byte
bdnzt eq,Lwordloop // loop if ctr!=0 and cr0_eq
beq Lleftovers // 0-byte not found in aligned words
// Found a 0-byte. Store last word up to and including the 0, a byte at a time.
// r8 = last word or doubleword, known to have a 0-byte
// r9 = dest ptr
Lstorelastbytes:
srgi. r0,r8,GPR_BYTES*8-8 // right justify next byte and test for 0
slgi r8,r8,8 // shift next byte into position
stb r0,0(r9) // pack into dest
addi r9,r9,1
bne Lstorelastbytes // loop until 0 stored
L0found:
sub r3,r9,r3 // get #bytes stored, including 0
subi r3,r3,1 // don't count the 0
blr // return strlen(src)
// 0-byte not found in aligned source words. There are up to GPR_BYTES-1 leftover
// source bytes, hopefully the 0-byte is among them.
// r4 = source ptr (aligned)
// r5 = leftover bytes in buffer (0..GPR_BYTES-1)
// r6 = 0xFEFEFEFF
// r7 = 0x80808080
// r8 = last full word or doubleword of source
// r9 = dest ptr (unaligned)
Lleftovers:
stg r8,0(r9) // store last word or doubleword
addi r9,r9,GPR_BYTES
addi r0,r5,1 // make sure r5 terminates byte loop (not r0)
b Lbyteloop
// Buffer full but 0-byte not found. Stuff a 0 into last byte of buffer.
// r3 = start of buffer
// r4 = ptr to next byte in source
// r9 = ptr to first byte past end of buffer
L0notfound:
sub. r3,r9,r3 // get #bytes stored, ie original buffer length
beq Lfind0 // skip if buffer 0-length
li r0,0 // get a 0
stb r0,-1(r9) // always store 0-byte unless buffer was 0-length
// Keep searching for 0-byte ending source, so we can return strlen(source).
// Not optimized, since this is an error condition.
// r3 = number of bytes already copied
// r4 = ptr to next byte in source
Lfind0:
lbz r0,0(r4) // get next byte
addi r4,r4,1
addi r3,r3,1 // increment strlen
cmpwi r0,0
bne Lfind0 // loop if not 0
subi r3,r3,1 // don't count the 0-byte
blr // return strlen(source)